Carburetor



Aug. 31 1926.

N. \N. UNDERWOOD CARBURETOR Filed August 24, 1925 [HI ll Patented Aug. 31, 1926.

UNITED STATES WALTER W. UNDERWOOD, OF SEATTLE, WASHINGTON.

CARB'UBETOR.

Application filed August 2 1, 1925. Serial .'1\To. 51,981.

My invention relates to improvements in carburetors for internal combustion engines and the object of my invent-ion is to provide a floatless carburetor of simple construction 5 that is efficient in operation, economical in its consumption of fuel, that is universally adaptable to all types of internal combustion engines and that will operate in the same manner regardless of its position.

Another object is to provide a: carburetor having a suction operated valve controlling the inlet of air and having means connected with and governed by the movement of said suction operated valve for controlling the opening and closing of a fuel inlet valve.

Another object is to provide choke means for varying the opening of the fuel inlet valve in proportion to the area of the opening of the air inlet ports, said choke means comprising a sleeve arranged to be rotated to close certain air inlet openings and to thereby cause valve operating means to open a fuel inlet valve wider.

Another object is to provide simple and eflicient means for admitting auxiliary or additional air to govern the richness of the fuel mixture.

Another object is to provide a carburetor having auxiliary air inlet means by which air may be admitted through the carburetor to the engine when the engine is running as when an automobile is running down hill while in gear and when the fuel is entirely shut off tocool the engine cylinders, eliminate carbon and serve as a brake when needed.

Other and more specific objects will be ap parent from the following description taken in connection with the accompanying drawings.

In the drawings Figure 1 is a view in elevation of a carburetor constructed in accordance with my invention.

Figure 2 is a view in vertical section of the same substantially onbroken line 2 2 of Fig. 1. p i

Fig. 3 is a top plan view of the same.

Fig. 4 is a sectional view on line H of Fig. 2. V

Fig. 5 is a detached view of the fuel inlet valve showing parts in plan and other parts in cross section.

' Like reference numerals designate like parts throughout the several views.

7 is a carburetor body having an upper M*"7?1W| tubularbore 8 and having a lower portion W1 9 of enlarged diameter that terminates at its bottom end in a convergent or conical portion 10. The usual butterfly or throttle valve 11 is provided in the bore 8 on a cross shaft or stem 12 that extends through ribs 13 on the body 7 and is provided on one end with an arm 14 to which suitable foot and hand throttle actuating means may be connected for opening and closing the throttle valve 11. The top of the carburetor body is suitably flanged as at 15 for connection to the inlet pipe or manifold of an internal combustion engine.

16 is a cylindrical tube or pipe that extends from the bottom of the carburetor body upwardly through the enlarged portion 9 and into the tubular bore 8. The tube 16' has lower air ports 17 and upper air ports 18 forming an important part of the air control means as hereinafter described.

20 is a rotatable sleeve that fits the exterior of the tube 16 and extends upwardly into the enlarged portion 9' of the carburetor body to a point above the upper ends of lower air ports 17. The sleeve 20 is provided near its lower end with a conical flange 21 that extends outwardly and upwardly from the lower port-ion'thereof and is adapted to fit snugly over the lower conical end 10 of the enlarged portion 9 of the carburetor body. Holes 22 are provided in flange 21 for registration or non-registration with holes 23 in conical body portion 10 to control the inlet of auxiliary air. The contacting surfaces of body portion 10 and flange 21 are ground to form, a substantially air tight fit and a packing nut 24 is provided at the bottom of sleeve 20 to prevent leakage of air. An integral arm 25 on f flange 21 is connected with push and pull wire 26 by which the sleeve 16 may be rotated. The sleeve 20 is provided with suitable openings 29, Fig. 4c, of greater dimensions than the lower air ports 17 in tube 16 that are adapted to register withor overlap to various degrees the air ports 17 to control the admission of air and to regulate the amount of movement of certain valves hereinafter described.

An annular chamber 27 for the passage of air is formed between the external walls of tube 16 and sleeve 20 and the internal walls of enlarged carburetor body portion 9.

An elbow member 28 fits over the bottom end of tube 16 and is preferably secured thereto by transverse taper pin 30; The top edges of the elbow member 28 is provided preferably at two diametrically opposite points with lugs 31 that are arranged at right angles to the key 30 and that bear against packing nut 24 so that the elbow member 28 serves to hold the sleeve 20 in assembled relation relative to the other parts of the carburetor.

32 is a fuel inlet tube extending diametrically crosswise of tube 16 and cylindrical bore 8 and provided with an enlarged externally threaded end 33 arranged to screw through flangeportion 13 of the carburetor body. A look nut 34 is provided on enlarged portion 33 of tube 32 and said enlarged portion 33 is adapted to be connected by suitable means, not shown, with a source of supply of liquid fuel as with a gasoline tank.

The fuel inlet tube 32 is internally recessed to form a valve chamber 35 for the the reception of a valve member 36 having at its forward end a needle valve 37 arranged to cooperate with a valve seat 38. A compression spring 39 tends to hold the needle valve 37 in a closed position.

40 is a wedge shaped cam that extends upwardly through openings 41 in the fuel inlet tube 32 and through openings 42 in the valve member 36 in such a manner as to move valve 36 and open needle valve 37 when said wedge member is moved upwardly. The valve member 36 is preferably notched or grooved longitudinally to permit fuel to be drawn past said valve member and-discharge through perforations 39. To simplify and cheapen construction the openings 41 may be in the form of a notch on a one side of tube 32 and the opening 42 in valve member 36 may be in the form of a notch on the opposite side of said valve member as shown in Fig. 5, said notches overlapping'to permit the wedge 40 to pass upwardly therethrough. The forward end of valve member 36 is small enough to permit the passage of fuel so thatsaid fuel may discharge both from the perforations 39 and notch 41;

The lower end of wedge 40 is adjustably connected by threads 43 and lock nut 44 with a valve disc 45 that fits snugly within tube 16 and is provided. with outwardly extending peripheral portions 46 that are guided within the air ports 17. spring 47 is interposed between valve disc 45 and fuel inlet tube 32 to urge said valve disc 45 downwardly to keep the extensions 46 seated on the bottom edges of air ports 17 when the carburetor is not in operation.

A vertically movable pin 48 extends from a'point near the lowermost position of valve disc 45 downwardly through the bottom of elbow member 28 so thatvalve disc 45 may be manually raised to open fuel inlet valve A compression 37 in adjusting the carburetor or when start ing the engine with which the carburetor is connected.

It will be noted that the upper end of the wedge 40 is provided with an incline or hump 49 slightly more abrupt than the remainder of said wedge to provide for the initial opening of'needle valve 47 for idling purposes as hereinafter described.

In the operation of this carburetor when the engine with which the carburetor is connected is not running the air valve 45 will be in its lowermost position and the needle valve 37 will be closed as shown in the Fig. 2. hen the valves 45 and 37 are thus closed the sleeve 20 will preferably be turned into the position shown in Fig. 4 so that air ports 17 and 29register fully and air ports formed by perforations 22 and 23 are entirely closed.

lVhen the engine is started suction exerted thereby will lift the air valve 45 thus opening the needle valve 47 and permitting both air and fuel to be drawn into the engine, the fuel being atomized and thorough ly mixed with the air to form an explosive mixture as it is drawn outof fuel inlet tube 32. The suction within the carburetor body will be controlled by the position of the throttle valve 11 and such suction will be relieved or offset by the passage of air inwardly through elbow member 28, tube 16. thence outwardly. through air ports 17 and 29, upwardly through passageway 27, in-

wardly through air ports 18 and, thence through tubular bore 8 to the inlet pipe of engine. tensity of the suction-controls the movement of air valve 45 and that movement of air valve 45 controls the opening and closing of air inlet ports 17 and also controls the opening and closing of fuel inlet valve 37 thus automatically providing means for varying the amount of fuel to correspond to the amount of air admitted.

When the carburetor is used on the engines ofmotor vehicles rotary movement of the sleeve 20' is preferably controlled manually by means located within easy reach of the driver of the vehicle so that suitable adiustment for different operating conditions may be readily made,

If, 'when the sleeve 20 is in the position shown in Figs. 2 and 4,the mixture is too rich then said sleeve may be rotated in a counter -,clockwise direction to cause auxiliary air inlet openings 22 to register with openings 23' and admit more air in proportion to the amount of fuel, it being apparent that when air is admittedthrough openings 22--23 the suction will be partially relieved bythis air and valve 45 will be permitted to partially close thus partially closing needle valve 37. i

I If the fuel mixture is found to be too lean It will thus'be'seen that the inthen the sleeve 16 may be rotated in a clock wise direction thus closing air inlet openings 22-23 and narrowing the air ports 17 by partially overlapping the same so that suction through carburetor body will raise the valve farther than it otherwise would to obtain a given amount of air and will thus open the needle valve 37 a greater amount and admit more fuel in proportion to the amount of air. In this way the narrowing of air ports 17 acts as choke means to secure a richer mixture without reducing the amount of air that will be drawn into the cylinders.

In starting an engine a rich mixture may be obtained by rotating the sleeve 20 until the ports 17 are relatively narrow. F or heavy pulling, the sleeve 20 may be adjusted to give the most efiicient mixture oi fuel and air. F or high speed and light pulling, as on down grades with motor vehicles, the openings 2223 may be opened to admit auxiliary air and give the most economical mixture, while for driving down hill with the motor vehicle in gear where no fuel is needed the sleeve 20 may be turned counter clockwise far enough to entirely open passageways 2223 and yet leave air ports 17 fully open thus admitting pure air to the cylinders which air will tend to cool the cylinders and reduce carbon deposits and may further be compressed within the en gine cylinders to increase the eiiiciency of the engine as a brake.

The foregoing description and accompanying drawings clearly disclose a preferred embodiment of my invention but it will be understood that this disclosure is merely illustrative and that such changes in the invention may be resorted to as are within the scope and spirit of the following claims.

I claim 1. In a carburetor, a body provided with a tubular portion having upper air ports and having lower air ports extending lengthwise in its walls, an enlarged body portion surrounding said tubular portion in spaced relation therefrom, and having air inlet openings, a sleeverotatable on said tubular portion and having longitudinally extending ports arranged to be moved into and out of registration with the lower air ports in said tubular portion, means on said sleeve having openings arranged to register with the openings in said enlarged body portion for admitting additional air to said enlarged body portion and a suction operated air valve movable lengthwise in said tubular portion.

2-. In a carburetor, a body provided with a tubular portion having upper air ports and having relatively long lower air ports extending lengthwise in its walls, an enlarged body portion surrounding said tubular portion and affording an annular air passage- Way around the exterior of said tubular portion, said enlarged body portion having air inlet openings near its bottomend, a sleeve rotatable on said tubular portion and terminating below said upper air ports, said sleeve having openings of greater width than the lower air ports in said tubular portion arranged to be moved into and out of registration with said lower air ports by rotary movement of said sleeve, a suction operated air valve movable lengthwise within said tubular portion and a flange rigid with said sleeve arranged to lit the lower end of said enlarged body portion said flange having holes arranged to be moved into and out of registration with the holes in said enlarged body portion by rotation of said sleeve.

The foregoing specification signed at Seattle, Washington this 8th day of August, 1925. 

